The present application relates to semiconductor technology, and more particularly to a semiconductor structure including a vertically integrated front-end-of-the-line (FEOL) metal-insulator-metal (MIM) capacitor that has a high capacitance density. The present application also relates to a method of forming such a semiconductor structure.
A capacitor is a passive two-terminal electrical component used to store electrical energy temporarily in an electrical field. The forms of conventional capacitors vary widely, but each capacitor contains at least two electrical conductors (i.e., plates) separated by a dielectric (i.e., an insulator) that can store energy by becoming polarized. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of an electrostatic field between its plates.
Metal-insulator-metal (MIM) capacitors represent one class of capacitors in which an insulator layer is sandwiched between a first conductive metal (i.e., first plate) and a second conductive metal (i.e., second plate). Conventional MIM capacitors are typically planar devices meaning that the first conductive metal is formed on a surface of a substrate, followed by the formation of the insulator layer on an exposed surface of the first conductive metal, and followed by the formation of the second conductive metal on an exposed surface of the insulator layer. Stated in other terms, the various components of a planar MIM are vertically stacked one atop another.
Moreover, MIM capacitors are typically formed in the back-end-of-the-line (BEOL). BEOL represents a second portion of an integrated circuit (IC) fabrication where the individual devices such as, for example, transistors, get interconnected with wiring on the wafer. The front-end-of-the-line (i.e., FEOL) is the first portion of IC fabrication where the individual devices such as, for example, transistors, are formed within and/or upon a semiconductor substrate.
In such capacitors, density is important in order to minimize the area occupied by the capacitors. Moreover, high quality dielectric-to-metal interfaces are needed in order to minimize capacitance variability.
In view of the above, there is need for providing a high density MIM capacitor that can be integrated into the FEOL rather than the BEOL, in which the dielectric-to-metal interfaces of such FEOL capacitors are of high quality.